The present invention relates to a stylus for use in recording signals on a lacquer disc or reproducing signals from the record, and in particular to an electrode including a layer of graphite integrally formed on a surface of a diamond body.
In video recording and reproducing systems of the grooveless capacitance detection type, as disclosed in commonly assigned U.S. Pat. No. 4,426,660, incorporated by reference herein, the cutting stylus is formed of a diamond body for cutting the surface of a lacquer disc to form minute pits along sprial or concentric tracks. The diamond body is provided with an electrode to release electrostatic charges which build up at the diamond tip as the result of the cutting. The reproducing stylus is also formed of a diamond body which rests over several tracks and the electrode reads just one information signal from each track of a disc record by sensing its geometric surface variations. It is required that the stylus be maintained in a stable contact relation with the surface of the disc which spins at a high speed. The electrode is conventionally formed by vacuum deposition, sputtering, or ion plating of a conductive material such as halfnium or titanium. Since the conductive material that forms the electrode is chemically different from the underlying body, the electrode, formed as a layer, is physically attached to the underlying body. This results in the electrode having the tendency toward separating from the underlying diamond body when subject to heat or friction which are likely to encounter during stylus manufacture or actual use. Another conventional method for making the electrode involves ion injection. Because of the strong bonding between carbon atoms that form the diamond body, it is difficult to inject enough ions to provide a highly conductive electrode.